JPH07195635A - Multilayered structure and production thereof - Google Patents

Abstract

PURPOSE:To impart beautiful appearance having no wavy patterns and to enhance gas barrier properties by molding a multilayered structure having three or more layers consisting of a polyolefinic resin layer having a specific melt index value and the like. CONSTITUTION:A multilayered structure having three or more layers consisting of a polyolefinic resin layer P, an ethylene/vinyl acetate copolymer layer E and a mixture layer M is molded. The layer M is composed of a mixture of a recovered substance such as molding loss or scrap at the time of the production of the multilayered structure and a resin B same to the resin of the layer P in kind and having a melt index different from that of the resin of the layer P. When the melt indexes of the resins of the layers P, E, B are set to Pm, Em and Bm, the relations of Bm > Em at the time of Em < Pm and Bm < Em at the time of Pm > Em are provided between the melt indexes of the respective resins and the respective melt indexes are displayed as values (g/10 min) measured at the same temp. of 190-230 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure having a beautiful appearance and excellent gas barrier properties, and a method for producing the same.

[0002]

2. Description of the Related Art A thermoplastic resin having excellent moisture resistance and mechanical properties, particularly saponified ethylene-vinyl acetate copolymer having excellent polyolefin layer and oxygen barrier properties (hereinafter referred to as EVO).
Multilayer plastic packaging material in which layers (referred to as (H)) are laminated via an adhesive resin, and can be used as containers with excellent oxygen barrier properties in the form of bottles, cups, pouches, etc. for various foods, cosmetics, medical chemicals, toiletries, etc. Widely used in the field. When manufacturing such a multi-layered plastic container, burrs due to pinch-off are inevitable in blow molding of bottles, etc. In the case of cup molding, molding loss parts such as punched scraps and regrind etc. and defective molding (scrap) are inevitable. , And its reuse is required from the viewpoint of cost and resource saving. In order to effectively reuse these molding loss parts such as burrs and regrinds and defective moldings (hereinafter, abbreviated as "collected materials"), (a) a polyolefin-based thermoplastic resin layer of a multilayer structure Method of mixing recovered materials for use (Japanese Patent Publication No. 59-2940)
9) (b) A method for molding a multi-layer parison in which a recovered material is interposed between a thermoplastic polyolefin resin and EVOH (Japanese Patent Laid-Open No. 59-101338) and the like have been proposed. However, in the case of (a), EVOH tends to deteriorate during simultaneous melt extrusion molding, and black deposits (burns) are generated inside the extruder during kneading melt extrusion, or adhere to die lips during extrusion. A gel-like substance (meyer), etc. is generated, which causes non-uniform phase-separated foreign matter or abnormal flow, which also deteriorates the appearance characteristics of the container, reduces the flavor due to the odor of resin decomposition products, impact resistance, etc. In reality, it is often the case that extrusion molding cannot be carried out practically at all, or even if it is possible, it can only be operated for a short period of time. In the case of (b), the same polyolefin as the main material polyolefin is mixed in the regrind to improve the adhesiveness between the main material layer and the regrind layer, but in the case of coextrusion molding In addition, a wavy pattern is generated on the surface of the molded product, and delamination is likely to occur between layers.
In addition, in order to improve the adhesiveness, compatibility, dispersibility, etc. of the polyolefin and EVOH, a resin composition obtained by modifying the polyolefin with maleic anhydride, glycidyl methacrylate, or the like may be used as a mixture with regrind. However, these modified resin compositions are expensive and cause problems in terms of cost.

[0003]

DISCLOSURE OF THE INVENTION The present invention aims to eliminate such charring, stains and abnormal flow that occur during extrusion molding, and to effectively reuse scrap compositions such as regrind. The object of the present invention is to obtain a molded product of a low-cost multilayer structure which has a beautiful appearance without a pattern and has an excellent gas barrier property.

[0004]

Therefore, the inventors of the present invention have formed a multi-layer structure including a resin layer containing a polyolefin resin as a main component and an ethylene-vinyl alcohol copolymer layer by blow molding. As a result of diligent studies aimed at effectively reusing the loss part and the scrap recovered product in the same molding system, as a result, in the desired multilayer structure, the recovered product and the main material polyolefin resin (P) are melted in the same kind. By mixing virgin polyolefin resins (B) with different indexes and extruding as a mixed layer with an extruder, a multilayer structure having almost the same appearance as that of the main material alone can be obtained, and the recovered material is molded into the same shape. They have found that they can be effectively reused in the system and reached the present invention.

That is, the present invention relates to a multilayer structure having three or more layers consisting of a polyolefin resin layer (P), an ethylene-vinyl alcohol copolymer layer (E) and a mixture layer (M). (M) has the following composition. (I) a recovered material (R) such as a molding loss portion or scrap generated when manufacturing this multilayer structure, and (ii) a polyolefin resin of the same kind as the above polyolefin resin (P), which has a melt index It is a mixture with different polyolefin resins (B). When the melt indexes of the resins P, E and B are Pm, Em and Bm, respectively, the melt indexes of the resins are selected from the following relational expressions (I) and (II). It is characterized by having two relationships. (I) When Em> Pm, Bm> Em, particularly preferably 2Em>Bm> 2Em-Pm. (II) When Pm> Em, Bm <Em, particularly preferably (Em + Bm) / 2>Bm> (Pm-Em)
/ 2. However, each melt index is 190-23
It is shown as a value (g / 10 minutes) measured at the same temperature within the range of 0 ° C.

The method for producing the multilayer structure of the present invention will be described in detail. First, the polyolefin resin (P) and the ethylene-vinyl alcohol copolymer (E) are extruded from the extruder as separate streams, A recovered material (R) obtained by crushing a molding loss portion or scraps generated when a multilayer structure having three or more layers is molded is obtained, and then the recovered material (R) and the polyolefin resin (P ) And a polyolefin resin (B) which is the same kind of resin and has a different melt index,
The method comprises coextruding with a polyolefin resin (P) and an ethylene-vinyl alcohol copolymer (E) to produce a multilayer structure having three or more layers, for example, a container such as a film, a sheet or a bottle. At that time, each of the resins P and E
The melt indexes of B and B are Pm and Em, respectively.
And Bm, each resin is selected and used so that each melt index satisfies one of the following relational expressions (I) and (II). (I) When Em> Pm, Bm> Em, particularly preferably 2Em>Bm> 2Em-Pm. (II) When Pm> Em, Bm <Em, and particularly preferably. Is (Em + Bm) / 2>Bm> (Pm-Em)
It has a relationship of / 2.

The resin [(P) or (B)] mainly composed of a polyolefin resin used in the present invention is mainly high density or low density polyethylene, polypropylene, polybutene-1, etc. and ethylene, propylene, butene-.
1, which is a copolymer of α-olefins selected from hexene-1, etc., and as a copolymer component with these α-olefins, diolefin, N-vinylcarbazole, vinyl chloride, vinylidene chloride, vinyl acetate , Vinyl compounds such as styrene, acrylonitrile, vinyl ether, unsaturated carboxylic acids such as maleic acid, acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid, itaconic acid or the acid component of such carboxylic acid and hydroxy or epoxy substituents Including those containing esters and acid anhydrides, for example, copolymers of graftable monomers and polyolefins and α-olefins /
It is also possible to use a copolymer having an α-olefin content of 50% by weight or more, such as an ionomer resin which is a reaction product of an α, β-unsaturated carboxylic acid copolymer and an ionic metal compound. In addition, the polyolefin resin-based resin layer is added in order to improve the adhesion between the polyolefin resin alone or a mixture of two or more polyolefin resins and the polyolefin resin layer and other thermoplastic resin. A thermoplastic resin other than the polyolefin-based resin described above is also included in a small amount, that is, a resin containing about 20% by weight or less is included. In the present invention, the polyolefin resin (B) which is the same kind as the polyolefin resin (P) and has a different melt index means, for example, when P is polypropylene, B is also polypropylene and has a different melt index from P.

The ethylene-vinyl alcohol copolymer (EVOH) used in the present invention has an ethylene content of 20-80.
It is a saponification product of ethylene-vinyl ester copolymer consisting of mol%, preferably 22 to 70 mol%, and the saponification degree of the vinyl ester component is preferably 80% or more, more preferably 85% or more and most preferably 90%. That is all. When the ethylene content is less than 20 mol%, the melt moldability is poor, and the gas barrier property and heat stability are poor. In the present invention EVOH
In some cases, it may be more preferable to blend and use one or more kinds of EVOH having different ethylene contents and / or saponification degrees. A typical vinyl ester is vinyl acetate, but other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used. Further, 0.0002 to 0.2 mol% of vinylsilane compound as a copolymerization component in EVOH
In the case where the EVOH is contained, the consistency of the melt viscosity between the base material and the EVOH is improved, and not only the homogeneous co-extruded multilayer film can be produced, but also the dispersibility is improved when the EVOH is blended and the moldability is improved. It is effective in terms of improvement. Examples of the vinylsilane compound here include vinyltrimethoxysilane, vinyltriethoxysilane,
Examples thereof include vinyltri (β-methoxy-ethoxy) silane and γ-methacryloxypropylmethoxysilane.
Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used. EVO used in the present invention
A suitable melt index of H is 0.1 to 50 g / 1.
0 minutes (when measured at 210 ° C. under a load of 2160), preferably 0.5 to 20 g / 10 minutes. Further, other copolymers [for example,
Propylene, butylene, unsaturated carboxylic acid or its ester {(meth) acrylic acid, (meth) acrylic acid ester methyl, ethyl), etc.}, vinylpyrrolidone (N-vinylpyrrolidone, etc.) can be blended.
Furthermore, it is also possible to blend a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, a filler, and other resins (polyamide, partially saponified ethylene-vinyl acetate copolymer, etc.) freely. In particular, as a measure for preventing gel formation, one or two or more of hydrotalcite-based compounds, hindered phenol-based, hindered amine-based heat stabilizers, metal salts of higher fatty acid carboxylic acids (for example, calcium stearate, magnesium stearate, etc.) are used. It is preferable to add 0.01 to 1% by weight.

It is also possible to add additives to the resins (P), (E) and (B) and their resin compositions. Examples of such additives may include antioxidants, UV absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, thermal stability improvers, or other polymeric compounds. However, these can be blended within a range in which the effects of the present invention are not impaired. The following are specific examples of the additive.

Antioxidants: 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis- (6-t-butylphenol), 2,2 '-Methylene-bis- (4-methyl-6-
t-butylphenol), octadecyl-3- (3 ′,
5'-di-t-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis- (6-t-butylphenol) and the like. UV absorber: ethylene-2-cyano-3,3'-diphenyl acrylate, 2- (2'-hydroxy-5'-
Methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl)
5-chlorobenzotriazole, 2-hydroxy-4-
Methoxybenzophenone, 2,2'-dihydroxy-4
-Methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone and the like. Plasticizer: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester, etc. Antistatic agent: pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins,
Polyethylene oxide, carbowax, etc. Lubricants: ethylene bis stearamide, butyl stearate, etc. Coloring agent: carbon black, phthalocyanine, quinacridone, indoline, azo pigment, red iron oxide, etc. Filler: glass fiber, asbestos, ballastonite, calcium silicate, etc. Also, many other polymer compounds can be blended to the extent that the effects of the present invention are not impaired.

The multilayer structure of the present invention comprises a polyolefin layer (P), an EVOH layer (E) and a mixed layer (M), and may contain an adhesive resin layer (A) as required. 3 layers P / M / E 4 layers P / M / A / E P / A / E / MP / E /
A / M 5 layers P / M / A / E / P P / A / E / A / M
P / M / A / E / M 6 layers P / M / A / E / A / P P / M / A / E / A
/ M 7 layers P / M / A / E / A / M / P

The adhesive resin used in the adhesive resin layer (A) shown here is not particularly limited, but a polyurethane-based or polyester-based one-component type or two-component type curable adhesive, Saturated carboxylic acid or its anhydride (maleic anhydride, etc.) is used as an olefin polymer or copolymer [polyethylene {low density polyethylene (LDP
E), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (SLDPE)}, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid ester (methyl ester or ethyl ester) copolymer]
Those grafted to are preferably used.

As the recovered product (R) of the multilayer structure in the present invention, the laminated body is used to form a molded product such as a hollow container, a tubular body, and a tubular packaging container obtained by further processing the tubular body. There is a molding loss part in the case of, and a crushed product of scrap collected after being used by general consumers.

When reusing the molding loss portion or scrap, the molding loss portion is mechanically crushed by applying an impact load with a rotary hammer or a rotary blade.
Generally, the crushed particles have an irregular shape, but a coarse shape, for example, a crushed particle having a length of 10 mm or more, is not preferable in consideration of charging into an extruder. The crushed molding loss part or scrap is then mixed with the same type of polyolefin resin as the polyolefin resin that forms the main material, but the melt index of the mixed polyolefin resin and the main material polyolefin resin is different. It is necessary. By this operation, a larger amount of the molding loss portion and scrap can be taken into the recovery layer than when the molding loss portion and the main material are generally mixed. Further, in the present invention, for the purpose of improving the compatibility of the polyolefin resin and EVOH, a mixture of polyolefin and EVOH or a resin composition obtained by adding a metal salt, an oxide, hydrotalcite, etc. to the above mixture is used as a molding loss part. It is also possible to mix it with a mixture of a virgin polyolefin resin.

The crushing and molding loss portion and the virgin polyolefin resin may be mixed by a mechanical means such as a Henschel mixer, or by a simple means in the hopper of the pushing machine, but either way. However, both must be intimately melt mixed in the extruder. That is, a molding loss portion, scrap, and a mixture of a virgin polyolefin-based resin of the same type as the main material mixed therein and having a different melt flow rate is supplied to the hopper of the extruder for molding the recovery layer, and the inside of the extruder If the mixing is insufficient, the unmelted material called fish eye will be generated and the transparency of the resin layer mainly composed of polyolefin resin will decrease, and not only the appearance will be markedly damaged but also interlayer adhesion The strength is also reduced, which is not preferable.
In order to perform intimate mixing, it is preferable that the temperature of the mixture in the extruder is equal to or higher than the melting temperature of the resin having the highest melting temperature in the mixture. The uniformly kneaded mixture becomes a multilayer structure by the multilayer molding method.

As a multilayer molding method, generally, the number of extruders corresponding to the type of resin layer is used, and coextrusion molding is performed in a layered state in which the flows of the resin melted in the extruder are superposed. The method carried out by so-called coextrusion molding is the best. As another method, a multilayer molding method such as extrusion coating or dry lamination can be adopted. Also obtained in this way,
Physical properties such as mechanical properties, gas barrier properties, etc. are further enhanced by carrying out uniaxial stretching, biaxial stretching, blow stretching, or other stretching of a multi-layer structure such as a parison, film or sheet, or by thermoforming. It is possible to obtain a container (bolts, cups, etc.) having Here, thermoforming means an operation in which a sheet is preliminarily softened by heating, then deformed by a plug and vacuum pressure and at the same time cooled to form a cup. Further, the heating may be a method in which the sheet is left at a temperature necessary for deformation for a predetermined time and operated so that the sheet is thermally substantially uniform. Various heaters may be used in consideration of operability. The method of uniform heating is preferable.

[0017]

【Example】

Example 1 Using a T-type die co-extrusion multilayer sheet manufacturing apparatus, co-extrusion was performed from three extruders at a cylinder temperature of 230 ° C., after being joined at a molten resin merging portion, extruded into a sheet form from a T-type die and cooled. As a result, a multilayer sheet having the following three-layer structure was obtained. PP (1) / AD (1) / EVOH / AD (1) / PP (1) Here, PP (1) is polypropylene J709HK manufactured by Ube Industries, Ltd. {melt index MI: 9 g / 10.
Min (230 ° C, 2160g)}, AD (1) is Admer QF570 manufactured by Mitsui Petrochemical Co., Ltd. {MI: 3.5g /
10 minutes (230 ° C., 2160 g)}, EVOH {ethylene content 32 mol%, saponification degree 99.6%, MI: 8 g /
10 minutes (230 ° C., 2160 g) was used. The obtained sheet was crushed into pellets with a pelletizer to give pellets having a diameter of about 5 mm. This crushed pellet virgin was PP (2) {Ube Industries Ltd.). Polypropylene J
815HK MI: 15g / 10 minutes (230 ° C, 216
0 g)} and a tumbler at a ratio of 7: 3.
(This pellet is abbreviated as “mixed pellet” hereinafter.) This extruder is another extruder (cylinder temperature: 230 ° C.) other than the three extruders of the T-die coextrusion multilayer sheet manufacturing apparatus. To 4 sheets, and simultaneously extruded from a total of four extruders, extruded into a sheet form from a T-type die at a molten resin merging portion, and cooled to obtain a multilayer structure of 7 layers of 4 types shown in Table 1. .

Example 2 A multilayer sheet of Table 1 was obtained in the same manner as in Example 1 except that the thickness of the mixed pellet layer in Example 1 was increased.

Example 3 PP (1) in Example 1 was replaced by PE (1) {Mirason B-16 MI manufactured by Mitsui Polychemical Co., Ltd .: 3.7 g /
AD (1) AD in 10 minutes (190 ° C, 2160g)}
(2) {Admer NF550 Mitsui Petrochemical MI: 1.
6g / 10 minutes (190 ° C, 2160g)}, PP
(2) PE (2) {Mirason B-324MI manufactured by Mitsui Polychemical Co., Ltd .: 1.3 g / 10 minutes (190 ° C., 2
160 g)} and a melt extrusion temperature of 190 ° C. was obtained in the same manner as in Example 1 to obtain a multilayer sheet of Table 1.

Comparative Example 1 Virgin PP (2) was added to the mixed pellets of Example 1.
A multilayer sheet of Table 1 was obtained in the same manner as in Example 1 except that was not added.

Comparative Example 2 PP (2) added in the mixed pellets in Example 1
PP (3) {Polypropylene J8 manufactured by Ube Industries, Ltd.
30HK MI: 30g / 10 minutes (230 ° C, 2160
g)} was changed to obtain the multilayer sheet of Table 1 in the same manner as in Example 1.

Comparative Example 3 A multilayer sheet of Table 1 was obtained in the same manner as in Example 3 except that PE (2) was not added to the mixed pellets in Example 3.

Comparative Example 4 PE (2) added into the mixed pellets of Example 3
PE (3) {Millason B-319 Mitsui Polychemical MI: 0.3 g / 10 minutes (190 ° C., 2160 g)}
The multilayer sheet of Table 1 was obtained in the same manner as in Example 3 except that

The multilayer structure (laminate) thus obtained was visually evaluated and the results shown in Table 1 were obtained.

[0025]

[Table 1]

The state of the film surface was evaluated according to the following criteria. Excellent: Uniform and good compatibility, no wavy pattern, and no phase-separated foreign matter. Excellent: A uniform and good compatibility is shown, but a small amount of phase-separated foreign matter is slightly observed in molding for a long time. There is no wave pattern. Good: The compatibility is good, but a slight amount of phase-separated foreign matter is observed. Acceptable: The compatibility is improved, but a slight amount of phase-separated foreign matter is observed. No: The compatibility is poor and foreign matter is seen. In addition, what is indicated by the symbol M in the column of the structure of the laminated body in Table 1 means a mixed pellet.

[0027]

As described above, the molded article of the multi-layer structure obtained by the method of the present invention is almost the same as the case where the virgin polyolefin resin is used although the molding loss portion is recycled. Since it has characteristics, the recycling of the molding loss portion can be achieved very effectively. Note that the molding loss portion generated during this recycling can be reused repeatedly by the same means. The present invention is an economically and socially promising means that can effectively recycle the molding loss portion of the multilayer structure in the same molding system, and also industrially, the amount of the molding loss portion generated. It has the advantages that the amount used can be easily adjusted, and that there is little moisture absorption and dust mixing in the molding loss portion. Further, according to the present invention, since the molding loss portion and the polyolefin resin can be uniformly mixed, the reuse of the molding loss portion improves the gas resistance and the liquid permeation barrier property as compared with the case where the virgin resin is used. It is possible to obtain a multilayer structure having an excellent appearance.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29K 105: 26

Claims (2)

[Claims] 1. A multi-layer structure comprising three or more layers consisting of a polyolefin resin layer (P), an ethylene-vinyl alcohol copolymer layer (E) and a mixture layer (M), which is a mixture layer (M). Is (i) a collected product (R) of a molding loss portion or scrap produced during the production of this multilayer structure, and (ii) a polyolefin resin of the same kind as the above polyolefin resin (P), which has a melt index If the melt index of each resin P, E and B is Pm, Em and Bm, the following relational expression ( I) and (II)
A multilayer structure having one relationship selected from the following: (I) When Em> Pm, Bm>Em; (II) When Pm> Em, Bm <Em However, each melt index is 190 to 23.
It is shown as a value (g / 10 minutes) measured at the same temperature within the range of 0 ° C. 2. A molding loss portion or scrap produced when a polyolefin resin layer (P) and an ethylene-vinyl alcohol copolymer (E) are extruded as separate streams from an extruder to form a multilayer structure. The mixture (M) obtained by mixing the recovered product (R) obtained by pulverization with a polyolefin resin (B) having the same kind of polyolefin resin as the above polyolefin resin but having a different melt index is used as a polyolefin resin. (P) and the ethylene-vinyl alcohol copolymer (E) are coextruded to produce a multilayer structure having three or more layers, the melt indexes of the resins P, E and B are respectively Pm, Em and Bm. Then, each resin should be selected and used so that each melt index has one relationship selected from the following relational expressions (I) and (II). (3) A method for producing a multi-layer structure comprising three or more kinds of the olefin resin layer (P), the ethylene-vinyl alcohol copolymer layer (E) and the mixture layer (M). (I) When Em> Pm, Bm>Em; (II) When Pm> Em, Bm <Em However, each melt index is 190 to 23.
Value measured at the same temperature within the range of 0 ° C (g / 10 minutes)